1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method for automatically discriminating whether a document is a color document or a black-and-white document, an image forming apparatus and a facsimile machine including the image processing apparatus, and a computer readable recording medium storing an image processing program.
2. Description of the Background Art
Some of color complex machines and color scanners have an automatic color document discrimination function of automatically discriminating whether a document is a color document or a black-and-white document based on image data obtained by scanning the document with an image reader. For example, a certain exemplary apparatus includes a mechanism which discriminates whether each pixel (or area) is chromatic color or achromatic color based on a predetermined threshold value from a plurality of color component signals of the pixel, and determines that the document is a color document if a ratio of chromatic pixels (or areas) to the total pixels (or total area) is larger than a predetermined threshold value. In other words, the document is determined to be a color document if the chromatic pixels (or areas) account for a predetermined area or larger on the document while being determined to be a black-and-white document unless otherwise. By controlling color/black-and-white copying (scanning) according to this determination result, a user needs not instruct color/black-and-white copying (scanning) for each document, whereby convenience is improved.
With the increase in the use of color complex machines and color printers in offices and the like in recent years, print outputs from color complex machines and color printers are more frequently used as documents to be copied/scanned.
With an increase in image quality of color complex machines, color scanners and printers, it has now become possible for anybody to easily obtain a copy true to a document image. This has led to a higher possibility of easily forging copy prohibited documents such as bank notes and valuable securities. Importance has been and is being placed on forgery prevention means to counteract against this and, as one of these, a technology is known which specifies information such as the manufacturer, model name and serial number of a machine used for copying or printing, output date and time by writing a normally invisible special code (tracking pattern) in an output itself. If a document shown in FIG. 5A for example is copied by a copier to which such a technology is applied, an output is made with a tracking pattern represented by an arrangement of small dots (each dot made of one pixel for instance) in a predetermined block superimposed on an image. The tracking pattern is generally formed of a yellow color material which is difficult to visually confirm.
The present invention is a further improvement of the above prior art.